The FIG. 6 shows the commonly used bottle having a filter at its discharging opening, which stores water-soluble drug as internal liquid (U.S. Pat. No. 2,711,922). In these common bottles, most of the water-soluble drug is stored in the bottom of the bottle after usage, while a little of it stays clinging on the inside face side of a discharging opening 100.    Patent document 1: The Japanese Patent Gazette No. 2711922.
In suchlike state, when the bottle is put upside-down and squeezed to discharge the water-soluble drug, the water-soluble drug staying on the inside face of the discharging opening 100 may be discharged including air in the bottle, and the air may form air bubbles. If the air bubbles are formed around the discharging opening 100 in the described manner, the water-soluble drug spatters around when the air bubbles burst. Therefore, to drop the water-soluble drug with accuracy is difficult. Additionally, once a big air bubble is formed, a hydrophilic filter containing water becomes a barrier. Thus it is impossible to drop the water-soluble drug without generating the high pressure over the bubble point of the filter. Or the water-soluble drug goes along the surface of the air bubble to the downside surface of it before the air bubble bursts, so that it becomes instable since more than anticipated amount of the drug solution will be dropped or the like thing will happen. Aforementioned structural problem is a crucial defect for medical instruments since the things especially like eye drops which is instilled into patients' eyes by doctors are required to be dropped quickly and precisely in a precise amount.